Measurements of Arterial Occlusion Pressure Using Hand-Held Devices.

ABSTRACT: Vehrs, PR, Reynolds, S, Allen, J, Barrett, R, Blazzard, C, Burbank, T, Hart, H, Kasper, N, Lacey, R, Lopez, D, and Fellingham, GW. Measurements of arterial occlusion pressure using hand-held devices. J Strength Cond Res 38(5): 873-880, 2024-Arterial occlusion pressure (AOP) of the brachial artery was measured simultaneously using Doppler ultrasound (US), a hand-held Doppler (HHDOP), and a pulse oximeter (PO) in the dominant (DOM) and nondominant (NDOM) arms of males ( n = 21) and females ( n = 23) using continuous (CONT) and incremental (INCR) cuff inflation protocols. A mixed-model analysis of variance revealed significant ( p < 0.05) overall main effects between AOP measured using a CONT (115.7 ± 10.9) or INCR (115.0 ± 11.5) cuff inflation protocol; between AOP measured using US (116.3 ± 11.2), HHDOP (115.4 ± 11.2), and PO (114.4 ± 11.2); and between males (120.7 ± 10.6) and females (110.5 ± 9.4). The small overall difference (1.81 ± 3.3) between US and PO measures of AOP was significant ( p < 0.05), but the differences between US and HHDOP and between HHDOP and PO measures of AOP were not significant. There were no overall differences in AOP between the DOM and NDOM arms. Trial-to-trial variance in US measurements of AOP was not significant when using either cuff inflation protocol but was significant when using HHDOP and PO and a CONT cuff inflation protocol. Bland-Altman plots revealed reasonable limits of agreement for both HHDOP and PO measures of AOP. The small differences in US, HHDOP, and PO measurements of AOP when using CONT or INCR cuff inflation protocols are of minimal practical importance. The choice of cuff inflation protocol is one of personal preference. Hand-held Doppler of PO can be used to assess AOP before using blood flow restriction during exercise.

Differences in Femoral Artery Occlusion Pressure between Sexes and Dominant and Non-Dominant Legs.

Background and Objectives: Blood flow restriction during low-load exercise stimulates similar muscle adaptations to those normally observed with higher loads. Differences in the arterial occlusion pressure (AOP) between limbs and between sexes are unclear. We compared the AOP of the superficial femoral artery in the dominant and non-dominant legs, and the relationship between blood flow and occlusion pressure in 35 (16 males, 19 females) young adults. Materials and Methods: Using ultrasound, we measured the AOP of the superficial femoral artery in both legs. Blood flow at occlusion pressures ranging from 0% to 100% of the AOP was measured in the dominant leg. Results: There was a significant difference in the AOP between males and females in the dominant (230 ± 41 vs. 191 ± 27 mmHg; p = 0.002) and non-dominant (209 ± 37 vs. 178 ± 21 mmHg; p = 0.004) legs, and between the dominant and non-dominant legs in males (230 ± 41 vs. 209 ± 37 mmHg; p = 0.009) but not females (191 ± 27 vs. 178 ± 21 mmHg; p = 0.053), respectively. Leg circumference was the most influential independent predictor of the AOP. There was a linear relationship between blood flow (expressed as a percentage of unoccluded blood flow) and occlusion pressure (expressed as a percentage of AOP). Conclusions: Arterial occlusion pressure is not always greater in the dominant leg or the larger leg. Practitioners should measure AOP in both limbs to determine if occlusion pressures used during exercise should be limb specific. Occlusion pressures used during blood flow restriction exercise should be chosen carefully.

Whole-Body Vibration as a Warm-up Before Exercise-Induced Muscle Damage on Symptoms of Delayed-Onset Muscle Soreness in Trained Subjects.

Magoffin, RD, Parcell, AC, Hyldahl, RD, Fellingham, GW, Hopkins, JT, and Feland, JB. Whole-body vibration as a warm-up before exercise-induced muscle damage on symptoms of delayed-onset muscle soreness in trained subjects. J Strength Cond Res 34(4): 1123-1132, 2020-There is no clear scientific evidence that whole-body vibration (WBV) used as a warm-up before performing eccentric exercise mitigates delayed-onset muscle soreness (DOMS) and speeds strength loss recovery. These benefits were observed primarily in nonresistance-trained individuals. The aim of this study was to determine whether WBV could mitigate soreness and expedite strength recovery for resistance-trained individuals when used as a warm-up before eccentric exercise. Thirty resistance-trained males completed 300 maximal eccentric contractions of the quadriceps after warming up with (WBV) or without (CON) WBV. Both CON and WBV experienced significant isometric (26.3 and 30.2%, respectively) and dynamic (50.9 and 46.4%, respectively) strength loss immediately after exercise. Isometric strength was significantly depressed after 24 hours in the CON group (8.2% p < 0.02), but not in the WBV group (5.9% p = 0.7). Isometric strength was no longer significantly depressed after 48 hours in the CON group (6.1% p < 0.07) or the WBV group (4.1% p = 0.20). Dynamic strength was significantly decreased in both the CON and WBV groups at 24 hours (17.7% p < 0.001 and 15.5% p < 0.001, respectively) and 48 hours (17.1% p < 0.01 and 13.6% p < 0.002), but only significant for the CON at 1 week after exercise (8.6% p = 0.05). Pain as measured by a visual analog scale was significant in both groups at 24 and 48 hours after exercise, but WBV experienced significantly less soreness than the CON group after 24 hours (28 vs. 46 mm p < 0.01, respectively) and 48 hours (38 vs. 50 mm p < 0.01). Pain pressure threshold increased significantly in both groups, but there was no difference between groups. These results suggest the use of WBV before eccentric exercise mildly mitigates DOMS in trained individuals. Application of WBV can function as a quick mode of warm-up before resistance training and can decrease pain perception from DOMS. This may be beneficial to athletes undergoing a heavy strength training phase where DOMS is likely.

Validity and Reliability of Standing Posture Measurements Using a Mobile Application.

OBJECTIVE: The purpose of this study was to evaluate the validity and reliability of standing posture assessments in asymptomatic men using the PostureScreen Mobile (PSM) iOS application. METHODS: The standing posture of 50 asymptomatic male participants (24.04 ± 1.81 years) was measured during 3 trials on the same day. The following 10 measurements using the PSM app were compared to the criterion VICON 3-dimensional analysis: from the frontal plane, shift and tilt of the head, shoulders, and hips; and from the sagittal plane, shift of the head, shoulders, hips, and knees. We used Bayesian methods to analyze the data. RESULTS: Compared with the VICON measurements, PSM assessments of head tilt, shoulder tilt and shift, and hip tilt and shift in the frontal plane were biased. In the sagittal plane, PSM measurements of shoulder, hip, and knee shift were biased. Only head shift in the frontal and sagittal planes were comparable between the VICON and the PSM. The VICON and PSM had similar intraclass correlations in 6 of 10 measurements. The PSM assessments of head shift and tilt and shoulder tilt in the sagittal plane were significantly less reliable than with VICON. CONCLUSION: The use of the PSM app introduced significant bias in postural measurements in the frontal and sagittal plane. Until further research reports additional validity and reliability data of the PSM app, we suggest caution in the use of PSM app when highly accurate postural assessments are necessary.

Heart rate and VO2 responses to treadmill running with body weight support using the GlideTrak™.

BACKGROUND/OBJECTIVE: The heart rate (HR) and metabolic (VO2) responses to treadmill running using the GlideTrak™ body weight support system have not been reported. The purpose of this study was to compare the submaximal and maximal HR and VO2 responses to normal-weight treadmill running (TMR) to treadmill running with body weight support provided by the GlideTrak™ (GTR). METHODS: Twenty participants (11 males; 9 females) 18 to 26 years of age voluntarily participated in this study. Each participant completed two exercise tests in each mode of running: a maximal graded exercise test to compare maximal HR and VO2 values and a submaximal exercise test to compare the HR-VO2 relationship. RESULTS: Maximal HR and VO2 values were significantly (p < 0.001) lower during GTR (183.4 ± 9.1 bpm, 38.1 ± 7.2 mL kg-1 min-1) compared to TMR (194.3 ± 8.6 bpm, 49.5 ± 8.9 kg-1 min-1). There was a significant difference in the HR-VO2 relationship between GTR and TMR. Compared to TMR, exercising at a HR of 140 bpm resulted in a VO2 that was 4.0 mL kg-1 min-1 lower during GTR. At the VO2 associated with a HR of 140 bpm during TMR, the HR during GTR was 16 bpm higher. During GTR at intensities of exercise up to an RER of 1.0, only 8 participants achieved vigorous intensities of aerobic exercise defined as 64-90% of VO2max. CONCLUSION: Exercising with the GlideTrak™ body weight support system may not provide the same cardiorespiratory training stimulus as normal-weight treadmill running.

HIV replication in CD4+ T lymphocytes in the presence and absence of follicular dendritic cells: inhibition of replication mediated by α-1-antitrypsin through altered IκBα ubiquitination.

Follicular dendritic cells (FDCs) increase HIV replication and virus production in lymphocytes by increasing the activation of NF-κB in infected cells. Because α-1-antitrypsin (AAT) decreases HIV replication in PBMCs and monocytic cells and decreases NF-κB activity, we postulated that AAT might also block FDC-mediated HIV replication. Primary CD4(+) T cells were infected with HIV and cultured with FDCs or their supernatant with or without AAT, and ensuing viral RNA and p24 production were monitored. NF-κB activation in the infected cells was also assessed. Virus production was increased in the presence of FDC supernatant, but the addition of AAT at concentrations >0.5 mg/ml inhibited virus replication. AAT blocked the nuclear translocation of NF-κB p50/p65 despite an unexpected elevation in associated phosphorylated and ubiquitinated IκBα (Ub-IκBα). In the presence of AAT, degradation of cytoplasmic IκBα was dramatically inhibited compared with control cultures. AAT did not inhibit the proteasome; however, it altered the pattern of ubiquitination of IκBα. AAT decreased IκBα polyubiquitination linked through ubiquitin lysine residue 48 and increased ubiquitination linked through lysine residue 63. Moreover, lysine reside 63-linked Ub-IκBα degradation was substantially slower than lysine residue 48-linked Ub-IκBα in the presence of AAT, correlating altered ubiquitination with a prolonged IκBα t(1/2). Because AAT is naturally occurring and available clinically, examination of its use as an inhibitory agent in HIV-infected subjects may be informative and lead to the development of similar agents that inhibit HIV replication using a novel mechanism.

Effect of Localized Vibration Massage on Popliteal Blood Flow.

There is a broad scope of literature investigating whole-body vibration (WBV) effects on blood flow (BF). However, it is unclear how therapeutic localized vibrations alter BF. Low-frequency massage guns are advertised to enhance muscle recovery, which may be through BF changes; however, studies using these devices are lacking. Thus, the purpose of this study was to determine if popliteal artery BF increases from localized vibration to the calf. Twenty-six healthy, recreationally active university students (fourteen males, twelve females, mean age 22.3 years) participated. Each subject received eight therapeutic conditions randomized on different days with ultrasound blood flow measurements. The eight conditions combined either control, 30 Hz, 38 Hz, or 47 Hz for a duration of 5 or 10 min. BF measurements of mean blood velocity, arterial diameter, volume flow, and heart rate were measured. Using a cell means mixed model, we found that both control conditions resulted in decreased BF and that both 38 Hz and 47 Hz resulted in significant increases in volume flow and mean blood velocity, which remained elevated longer than the BF induced by 30 Hz. This study demonstrates localized vibrations at 38 Hz and 47 Hz significantly increase BF without affecting the heart rate and may support muscle recovery.

Trends in BMI Percentile and Body Fat Percentage in Children 12 to 17 Years of Age.

This study evaluates the cross-sectional trends in body fat percentage (BF%) and body mass index (BMI) percentile rank, and the relationship between the two in 332 (177 boys, 155 girls) 12- to 17-year-old children. Body mass index (BMI) was calculated using measured height and body mass, and sex-specific BMI for age percentile rank was determined using CDC growth charts. Body fat percentage (BF%) was measured with DEXA. Fat mass index (FMI) and fat-free mass index (FFMI) were calculated by normalizing the fat mass and fat-free mass for height. Compared to boys of the same age, girls had significantly higher BF% and FMI values and lower FFMI values. Compared to boys, at a given BMI percentile rank, females had a higher BF% and FMI, and a lower FFMI. In both boys and girls, there was an exponential increase in adiposity above the 70th percentile rank. BMI percentile rank is not an equivalent indicator of body fatness in boys and girls. Other measures of body composition can further inform the practitioner of a child's adiposity.

Bayesian Analysis of the HR-VO2 Relationship during Cycling and Running in Males and Females.

Professional organizations advise prescribing intensity of aerobic exercise using heart rate reserve (%HRR) which is presumed to have a 1:1 relationship with either maximal oxygen uptake (%VO2max) or %VO2 reserve (%VO2R). Even though running and cycling are popular modes of training, these relationships have not been investigated in a group of males and females during both running and cycling. This study evaluated the %HRR-%VO2max and %HRR-%VO2R relationships in 41 college-aged males (n = 21) and females (n = 20) during treadmill running and cycling. Heart rate (HR) and VO2 data were collected at rest and during maximal exercise tests on a treadmill and cycle ergometer. The HR and VO2 data were analyzed using a Bayesian approach. Both the %HRR-%VO2max and %HRR-%VO2R relationships did not coincide with the line of identity in males and females in both treadmill running and cycling. %HRR was closer to %VO2max than to %VO2R. There were no significant differences in the intercepts of the %HRR-%VO2max and %HRR-%VO2R relationships between males and females during running or cycling, or between running and cycling in males or females. The credible intervals of the intercepts and slopes suggest interindividual variability in the HR-VO2 relationship that would yield significant error in the prescription of intensity of aerobic exercise for an individual.

Simultaneous determination of equilibrium constants and enthalpy changes by titration calorimetry: Methods, instruments, and uncertainties.

Calorimetric methods have been used to determine equilibrium constants since 1937, but no comprehensive review of the various calorimeters and methods has been done previously. This article reports methods for quantitative comparison of the capabilities of calorimeters for simultaneous determination of equilibrium constants and enthalpy changes, for determining optimal experimental conditions, and for assessing the effects of systematic and random errors on the accuracy and precision of equilibrium constants and enthalpy changes determined by this method.

The Effects of Exercise on ß-Hydroxybutyrate Concentrations over a 36-h Fast: A Randomized Crossover Study.

PURPOSE: This study assessed ß-hydroxybutyrate (BHB) concentration during a short-term fast and the degree to which an initial bout of exercise influences the rate of ketogenesis. METHODS: Twenty subjects (11 male, 9 female) completed two 36-h fasts, with one protocol requiring the subject to complete a treadmill exercise session at the beginning of the fast. BHB levels were assessed via portable meter every 2 h, along with mood and hunger ratings. Venipuncture was performed every 12 h. RESULTS: The mean (SD) areas under the curve for BHB concentration were 19.19 (2.59) mmol·L-1 (nonexercised) and 27.49 (2.59) mmol·L-1 (exercised), yielding a difference of 8.30 mmol·L-1 between conditions (95% posterior probability interval (PPI), 1.94 to 14.82 mmol·L-1; posterior probability (PP) = 0.99). The mean (SD) times to BHB concentration of 0.5 mmol·L-1 were 21.07 (2.95) h (nonexercised) and 17.5 (1.69) h (exercised), a 3.57-h difference (95% PPI, -2.11 to 10.87 h; PP = 0.89). The differences in area under the curve between conditions were 5.07 µU·mL-1 (95% PPI, -21.64 to 36.18 µU·mL-1; PP = 0.67) for insulin, 97.13 pg·mL-1 (95% PPI, 34.08 to 354.21 pg·mL-1; PP = 0.98) for glucagon, and 20.83 (95% PPI, 4.70 to 24.22; PP = 0.99) for the insulin/glucagon ratio. CONCLUSIONS: Completing aerobic exercise at the beginning of a fast accelerates the production of BHB throughout the fast without altering subjective feelings of hunger, thirst, stomach discomfort, or mood. Insulin and the insulin/glucagon ratio experience a marked reduction within the first 12 h of fasting and was not altered with exercise. Thus, exercising at the beginning of a fast may improve the metabolic outcomes of fasting.

Two steps for scoring a point: Creating and converting opportunities in invasion team sports.

In invasion team sports, scoring efficiency depends on the ability to create scoring opportunities and to convert them into goals or points. Scoring performance varies across sports and comparisons among them are little. In this paper we compare creation and conversion of scoring opportunities in different team sports and genders. Box-score data from six sports [basketball, handball, water polo, field hockey, football, ice hockey] (328 teams, 5723 games, both genders) were standardized by "per ball possession". We applied Bayesian methods to compute the posterior distributions of shots per possession (SHTpPOS), points per shot (PTSpSHT) and points per possession (PTSpPOS). We evaluated differences for these three variables among sports, between genders and the correlation between every pair of them. Inter-sports evaluation evidenced basketball, handball, ice hockey and water polo are sports with a high probability of creating shots (SHTpPOS-p(robability) > 0.65). Complementary, ice hockey, field hockey and football are sports with a low probability of converting shots (PTSpSHT-0.05 < p < 0.26). Despite the distinct results among sports for creating and converting opportunities, all sports in both genders, converged to a scoring efficiency (PTSpPOS) below 0.5. In the genders' comparison, men are more efficient in creating opportunities than women, except in water polo. For scoring efficiency, differences between men and women are fewer. Results prevent generalization about differences in scoring efficiency between genders. Finally, creation and conversion have low correlation in sports with high shot creation probabilities (basketball and ice hockey). In these sports, scoring is not limited by the number of shots taken but rather by their accuracy. For sports with low shot creation probabilities (soccer and men field hockey), creation and conversion presented higher correlation. Evidences contribute to increase coaches' understanding about scoring tactics' challenges in team sports and design practices accordingly.

Effects of boil-and-bite and custom-fit mouthguards on cardiorespiratory responses to aerobic exercise.

BACKGROUND: The physiological responses to exercise when wearing a mouthguard may depend on the type of mouthguard and the facemask used during exercise testing. This study compared the effects of boil-and-bite (BBMG) and custom-fit (CFMG) protective mouthguards on the metabolic, cardiovascular, and ventilatory responses to exercise when wearing a facemask that allowed mouth only or nose and mouth breathing. METHODS: Twenty-four male college Lacrosse players (mean = 20±2 years) participated in this study. Each participant performed six submaximal exercise tests while wearing one of two facemasks (mouth only breathing and nose and mouth breathing) and one of three mouthguard conditions (BBMG, CFMG, no mouthguard). Steady-state VO2, rate of perceived exertion (RPE), tidal volume (VT), respiratory rate (RR), minute ventilation (VE), and heart rate (HR) values were measured at intensities of exercise corresponding to 60% and 80% of VO2peak. RESULTS: There were significant main effects for facemask type (mouth only breathing vs. nose and mouth breathing) for VO2, VE, VT, and RPE. There were significant main effects for mouthguard (BBMG, CFMG, and no mouthguard) for VO2, VE, RR, and HR. There were also multiple significant interactions. All of the differences in VO2, HR, VE, VT, RR, and RPE, although statistically significant, were negligible and of little practical significance. CONCLUSIONS: The physiological responses to wearing a BBMG or CFMG are of little practical significance so they can be worn to reduce the likelihood of dental injuries without impeding metabolic, cardiovascular and ventilatory responses.

Preseason Screen Cannot Predict Injury over Three Years of College Football.

PURPOSE: This study aimed to investigate if the Functional Movement Screen (FMS) total score, individual component test scores, or number of asymmetries can predict noncontact injury risk over three consecutive seasons of National Collegiate Athletic Association Division I football. METHODS: Because football teams comprise individuals with vastly different physical characteristics and playing responsibilities, we divided the subjects into three homogeneous groups based on position (big, combo, and skill). Each FMS score was assessed with regard to the total team score and by individual position groups. For our injury analysis, we also controlled for exposure. Two hundred and eight National Collegiate Athletic Association Division I athletes participated over three consecutive seasons, yielding a total of 343 observations. RESULTS: There was no significant relationship between total FMS score and likelihood of injury when analyzed by the total team or by position group. These findings were the same for all groups, for both the total number of injuries and injuries weighted by injury exposure. The only significant findings occurred when we considered individual test item scores to injury by position group. We only found a significant relationship in the expected direction with push-up stability in the combo group. CONCLUSIONS: FMS was not a good predictor of noncontact injury.

Effects of a 4-week exercise program on balance using elastic tubing as a perturbation force for individuals with a history of ankle sprains.

STUDY DESIGN: Randomized controlled trial with pretraining, posttraining, and follow-up repeated measures. OBJECTIVE: To determine the effectiveness of a 4-week elastic resistance exercise program on balance in subjects with and without a history of sprained ankles. BACKGROUND: Several researchers have suggested that improving balance may help alleviate the symptoms of functional ankle instability and reduce the rate of recurrent ankle sprains. METHODS AND MEASURES: Forty subjects (20 males, 20 females; 20 subjects with chronic ankle instability [CAI], 20 healthy) participated in the study. Ten subjects (5 males, 5 females) from each CAI and healthy group were randomly assigned to either the exercise or control group, resulting in a total of 4 groups. Total travel distance of the center of pressure, monitored using a force platform, was measured before training, after 4 weeks of training, and at a 4-week follow-up. RESULTS: There were no interactions between gender, ankle sprain history, or training groups. Balance significantly improved in subjects with and without a history of ankle sprains following 4 weeks of elastic resistance exercises. Mean improvement in balance for the exercise group following training, reflected through a decrease in total travel distance, was -11.1 cm (95% confidence interval: -14.0 to -8.2 cm). These improvements in balance were retained 4 weeks after training. CONCLUSIONS: Balance was improved after 4 weeks of elastic resistance exercise in subjects with and without a history of lateral ankle sprains. Balance improvements persisted 4 weeks following the treatment cessation.

Efficiency and productivity evaluation of basketball players' performance

Abstract Aim: Basketball players' performances have been traditionally summarized in indices that rely on the game-related statistics (e.g. rebounds, field goals, etc). Indices are defined according to different methods (e.g. Efficiency Index - Ei, Plus-Minus, Wins Produced), seeking distinct analytic objectives. Ei is frequently used given its simplicity. However, it has questionable validity since it measures productivity instead of efficiency and uses biased calculations for scoring. This study aimed to define indices of efficiency (Basketball Efficiency Index (BEi)) and productivity (Basketball Productivity Index (BPi)) of a player's contribution to the team performance with greater validity than Ei. Methods: We gathered public NBA game-related statistics (2014/2015 - 2018/2019). We analyzed: Ei's and BEi's winning prediction accuracy; Ei's and BEi's point spread prediction accuracy; the correlation between GRS and Ei, BEi, BPi, and PER; players' rank correlation between indices. Results: In comparison to Ei, both BEi and BPi reduced the weight of points scored on the final value. Less reliance on points scored results in a more accurate comparison of the contribution of players independent of their tactical roles. Conclusion: These indices may improve coaches' understanding of the real contribution of each player to team performance.

Understanding the complete pathophysiology of chronic mild to moderate neck pain: Implications for the inclusion of a comprehensive sensorimotor evaluation.

BACKGROUND: Inconsistencies in the literature concerning the effect of neck pain have led to a lack of understanding concerning the complete pathophysiology of neck pain. While the effect of neck pain on motor function as measured by active range of motion and isometric neck strength is well documented the effect of neck pain on sensory measures such as tactical acuity and neck reposition error (NRE) remain poorly understood. OBJECTIVE: The purpose of this study was to evaluate a combined sensorimotor evaluation to explore the potential benefits of incorporating both sensory and motor task into a physical evaluation of neck pain suffers to gain an added knowledge of the complete pathophysiology of their health status. METHODS: A cross-sectional study that measured neck joint reposition error, tactical acuity, neck isometric strength and range of motion in 40 volunteer participants (22 pain, 18 control). RESULTS: A statistically significant increase in NRE in flexion (2.75∘± 1.52∘ vs. 4.53∘± 1.74∘ and in extension (3.78∘± 1.95∘ vs 5.77∘± 2.73∘ in participants suffering from neck pain was observed. Additionally, the dermatome C5 was found to be the most affected. No differences were found in neck strength or neck range of motion between healthy controls and patients with chronic moderate neck pain.

Validity and Reliability of Assessing Body Composition Using a Mobile Application.

PURPOSE: The purpose of this study was to determine the validity and reliability of the LeanScreen (LS) mobile application that estimates percent body fat (%BF) using estimates of circumferences from photographs. METHODS: The %BF of 148 weight-stable adults was estimated once using dual-energy x-ray absorptiometry (DXA). Each of two administrators assessed the %BF of each subject twice using the LS app and manually measured circumferences. A mixed-model ANOVA and Bland-Altman analyses were used to compare the estimates of %BF obtained from each method. Interrater and intrarater reliabilities values were determined using multiple measurements taken by each of the two administrators. RESULTS: The LS app and manually measured circumferences significantly underestimated (P < 0.05) the %BF determined using DXA by an average of -3.26 and -4.82 %BF, respectively. The LS app (6.99 %BF) and manually measured circumferences (6.76 %BF) had large limits of agreement. All interrater and intrarater reliability coefficients of estimates of %BF using the LS app and manually measured circumferences exceeded 0.99. CONCLUSIONS: The estimates of %BF from manually measured circumferences and the LS app were highly reliable. However, these field measures are not currently recommended for the assessment of body composition because of significant bias and large limits of agreements.

Statistical models for multilevel skewed physical activity data in health research and behavioral medicine.

OBJECTIVE: Researchers who study physical activity often use outcome variables that have a lower bound of zero and are positively skewed (e.g., minutes of physical activity in a day). Researchers also often use statistical methods that assume the outcome is normally distributed or transform the outcome as an attempt to make it more normal, both of which can be problematic. In this article, the authors describe multilevel 2-part models that use a mixture of logistic regression-to predict whether a person was active-and gamma regression-to predict amount of activity if there was activity. METHOD: The authors contrast the 2-part models to a linear multilevel model using data from a longitudinal study of physical activity (N = 113; 2,305 observations). The dependent variable was minutes of moderate-to-vigorous activity in a day and the predictor variables were day, satisfaction, and gender. RESULTS: The 2-part models outperform the linear model and provide researchers critical information that is conceptually relevant, such as distinguishing between predictors of whether activity occurred and of how much activity occurred. CONCLUSIONS: Two-part models represent a flexible and useful addition to the analysis repertoire of health researchers. To assist researchers in learning these methods, the online supplemental materials provide additional technical information as well as annotated computer code for estimating these models. (PsycINFO Database Record

Prediction of VO2max in Children and Adolescents Using Exercise Testing and Physical Activity Questionnaire Data.

PURPOSE: The purpose of this study was to evaluate the use of a treadmill walk-jog-run exercise test previously validated in adults and physical activity questionnaire data to estimate maximum oxygen consumption (VO2max) in boys (n = 62) and girls (n = 66) aged 12 to 17 years old. METHODS: Data were collected from Physical Activity Rating (PA-R) and Perceived Functional Ability (PFA) questionnaires, a walk-jog-run submaximal treadmill exercise test, and a maximal graded exercise test. RESULTS: Regression analysis resulted in the development of 2 models to predict VO2max. Submaximal exercise test data were used to build the following model (R2 = .73; SEE = 4.59 mL + kg(- 1) + min(- 1)): VO2max (mL + kg(- 1) + min(- 1)) = 26.890+(5.877 × Gender; 0 = female; 1 = male) - (0.782 × Body Mass Index [BMI])+(0.438 × PFA Score) +(2.712 × Treadmill Speed; mph) +(0.746 × Age) +(0.449 × PA-R Score). Maximal exercise test data were used to build the following model (R2 = .83; SEE = 3.63 mL + kg(- 1) + min(- 1)): VO2max (mL + kg(- 1) + min(- 1)) = 10.716+(1.334 × Maximal Treadmill Grade) +(5.203 × Treadmill Speed; mph) +(3.494 × Gender; 0 = female; 1 = male) - (0.413 × BMI) +(0.249 × PFA). CONCLUSIONS: The results of this study demonstrate, for the first time, that regression equations that use both exercise data and physical activity questionnaire data can accurately predict VO2max in youth. The submaximal and maximal exercise tests that use self-selected treadmill speeds can be used to assess cardiorespiratory fitness of youth with a wide range of fitness levels.